I've finished Max Tegmark's fascinating "Our Mathematical Universe," a book I blogged about before here. The final chapter was a bit of a letdown. Tegmark ambled off into extraneous subjects, like how Earth might come to its demise and whether other conscious entities exist in the universe.
Surprisingly, Tegmark thinks we humans probably are the most intelligent life-form in the universe. If true, and I doubt that it is, that's depressing. Geez, 14 billion years have passed since the Big Bang, and Homo sapiens are the most sapient entities the cosmos could come up with?
But I still enjoyed the book.
I'm fascinated by the notion that existence exists, though I readily admit that if the opposite was true -- if existence didn't exist -- nobody would be around to know it. So I've come to feel that the pertinent question isn't "Why is there something rather than nothing?" but a statement: "There is something rather than nothing."
Tegmark's Mathematical Universe Hypothesis, MUH, is compatible with this way of looking at existence. Here's some excerpts from his book:
The MUH says that a mathematical structure is our external physical reality, rather than being merely a description thereof. This equivalence between physical and mathematical existence means that if a mathematical structure contains a self-aware substructure, it will perceive itself as existing in a physically real universe, just as you and I do (albeit generically a universe with different properties from ours).
Stephen Hawking famously asked, "What is it that breathes fire into the equations and makes a universe for them to describe?"
In the context of the MUH, there's thus no fire-breathing required, since the point isn't that a mathematical structure describes a universe, but that it is a universe. Moreover, there's no making required either. You can't make a mathematical structure -- it simply exists. It doesn't exist in space and time -- space and time may exist in it.
In other words, all structures that exist mathematically have the same ontological status, and the most interesting question isn't which ones exist physically (they all do), but which ones contain life -- and perhaps us.
Many mathematical structures -- the dodecahedron, for example -- lack the complexity to support any kind of self-aware substructures, so it's likely that the Level IV multiverse resembles a vast and mostly uninhabitable desert, with life confined to rare oases, bio-friendly mathematical structures such as the one we inhabit.
...When talking about parallel universes, we distinguished between four different levels: Level I (other such regions far away in space where the apparent laws of physics are the same, but where history played out differently because things started out differently), Level II (regions of space where even the apparent laws of physics are different), Level III (parallel worlds elsewhere in Hilbert space where quantum reality plays out) and Level 4 (totally disconnected realities governed by different mathematical equations).
Far-out ideas. And this barely scratches the surface of the strangeness, all supported by theories of modern physics, that Tegmark describes in his book.
I have no idea if what he says is true.
However, at least Tegmark backs up his hypotheses with scientific reasoning and facts. So if someone is attracted to mind-blowing cosmic possibilities, which I am, he or she is a lot better off embracing far-out physics than far-out religiosity.